Question

when alkali metals dissolves in liquid ammonia, the solution can acquire different colours. explain the reason.

Answer 1

All alkali metal dissolve in liquid ammonia giving deep blue solutions which are conducting in nature. These solutions contain ammoniated cations and ammoniated electrons as shown below:
M + ( x + y ) NH3 → M+(NH3 )x + e-(NH3)y
The blue colour of the solution is considered to be due to ammoniated electrons which absorb energy corresponding to red region of the visible light for the their excitation to higher energy levels. The transmitted light is blue which imparts blue colour to the solutions

Answer 2

The alkali metals like Na,K etc. dissolved in liquid Ammonia giving deep blue coloured solution.This solution is highly conducting in nature.It contains a large amount of Ammoniated captions as well as electrons as shown below in the reaction:-M + ( a + b )NH3 => M* ( NH3 )a + e(NH3)bIt has been found that the blue colour of solution is mainly due to the presence of the Ammoniated electrons in the solution.These electrons absorb energy corresponding to the red region of the visible light spectrum for its excitation to the higher energy levels.The transmitted light is blue coloured, thus it imparts blue colour to the solution.The solution is paramagnetic due to the presence and in the absence of catalysts and impurities decomposes the blue coloured solution and it gives formation to "Metal amide" and liberation of hydrogen gas.